THE HUBBLE SPACE TELESCOPE
No other orbiting telescope has generated as much excitement or so astounded astronomers.
Launched in April 1990, the Hubble Space
Telescope (HST) has provided spectacular observations in visual, near-infrared, and ultraviolet wavelengths, as well as spectroscopic studies of stars, the thin interstellar gas, and galaxies. Consisting of a 95 inch (2.4 m) mirror and a suite of sensitive scientific instruments, it is controlled by some 400 astronomers, computer scientists, and technicians.
The Wide Field/Planetary Camera II, the most often used of HST's instruments, can detect objects as faint as 28th magnitude (about a billion times fainter than can be seen with the naked eye). The Faint Object Camera can also record 28th magnitude stars, but it offers higher resolution and a wider choice of viewing angles. It can distinguish between objects a mere 0.05 arcsecond apart (the naked eye can only split objects 60 arcseconds apart).
Two newer instruments, installed in February 1997, are the Near Infrared Camera and Multi-Object Spectrometer (NICMOS), and the Space Telescope Imaging Spectrograph (STIS). NICMOS handles both imaging and spectroscopic observations of objects at near-infrared wavelengths. Scientists hope to learn much from these observations about the birth of stars in dense, dusty globules, the infrared emission produced by the active centers of distant galaxies, and the nature of a class of galaxies as bright as quasars at infrared wavelengths.
The STIS is considered the most complex scientific instrument ever designed for space. It covers a broader wavelength range than its predecessor, and can block out, or occult, the light of distant stars to search for black holes and Jupiter-size planets in other galaxies.
Finally, HST's fine-guidance sensors, necessary for pointing the telescope and locking onto its target, can measure the positions of stars to 0.002 arc-second. Such precision enables astronomers to note slight wobbles in a star's position, which might indicate the gravitational tug of an unsees planet- and the existence of other solar systems.